Energy Balance of the Earth
Physics: AQA GCSE Higher, topic 6.6.7
Energy Balance of the Earth
There is a balance between heat energy absorbed by the Earth and emitted by the Earth. This balance keeps the Earth at a stable temperature.
Heat absorbed (entering the Earth)
- 340 Watts per square metre of solar energy falls on the Earth.
- 29% is reflected back into space - primarily by clouds, but also by other bright surfaces and the atmosphere itself.
- About 23% of incoming energy is absorbed in the atmosphere by atmospheric gases, dust, and other particles.
- The remaining 48% is absorbed at the surface.
Heat emitted (leaving the Earth)
- Absorbed sunlight is balanced by heat radiated from Earth’s surface and atmosphere.
- Most heat escapes from areas just north and south of the equator, where the surface is warm, but there are few clouds.
- Along the equator, persistent clouds prevent heat from escaping.
- Likewise, the cold poles radiate little heat.
Test yourself on Energy Balance of the Earth
What percentage of the energy which reaches the Earth is reflected back into space?